Method for assembling a rotary apparatus with gap-controlling features

ABSTRACT

A rotary apparatus, such as a pneumatic motor, is disclosed. The rotary apparatus comprises an end plate having a race cavity, a main rotor with a stub shaft extending from one end, and a bearing, which includes an outer race seated in the race cavity and an inner race having a central bore. The stub shaft is fitted into the central bore with a frictional fit. In a preferred embodiment, the threaded shank of a screw is threaded into a threaded socket in the stub shaft so as to draw the stub shaft into the central bore with a washer bearing against the screw head, against the stub shaft, and against the inner race, whereby a controlled gap is provided between an outer surface of the main rotor and an inner surface of the end plate. In an alternative embodiment, a threaded nut is threaded onto a threaded stud extending from the stub shaft so as to draw the stub shaft into the central bore with a washer bearing against the threaded nut, against the stub shaft, and against the inner race, whereby the controlled gap in provided. Also, a related method for assembling the rotary apparatus is disclosed, in a preferred mode for assembling the preferred embodiment and in an alternative mode for assembling the alternative embodiment.

TECHNICAL FIELD OF THE INVENTION

This invention pertains to a rotary apparatus of a type comprising astatic structure, a rotary structure, and a bearing interposed betweenthe static and rotary structures, as exemplified by a pneumatic motor.This invention provides the rotary apparatus with novel features forproviding a controlled gap between a main rotor and an end plate. Thisinvention also pertains to a related method for assembling such anapparatus.

BACKGROUND OF THE INVENTION

Commonly, the static structure of a rotary apparatus of the type notedabove includes an end plate, which has a cavity to accommodate a bearingrace. It is convenient to refer to the cavity as a race cavity.

Commonly, the rotary structure thereof includes a main rotor and a stubshaft extending from one end of the main rotor, and the bearing includesan outer race seated in the race cavity of the end plate and an innerrace having a central bore to accommodate the stub shaft, which is sizedso as to be inserted into the central bore with a frictional fit.Commonly, the bearing is a rolling contact bearing including pluralrolling elements interposed between the outer and inner races, asexemplified by a ball bearing.

Heretofore, it has been common for the outer race of the bearing to bepress-fitted into the race cavity and for the stub shaft to bepress-fitted into the central bore of the inner race by means of ahydraulic or mechanical press. Generally, it is satisfactory to employ ahydraulic or mechanical press to press the outer race properly into therace cavity, as it can be easily ascertained when the outer race hasfully been pressed into the race cavity.

However, it is difficult to employ a hydraulic or mechanical press topress the stub shaft properly into the inner race, an it is necessary toprovide a gap within a narrow range of tolerances (such as for example,0.10 mm) between the main rotor and the end plate for proper operationof the rotary apparatus. It may then be necessary to employ gauges toassure a gap has been provided therebetween which falls within such arange.

SUMMARY OF THE INVENTION

This invention provides a rotary apparatus of the type noted above,which defines an axis and comprises a static structure, a rotarystructure, and a bearing interposed between the static and rotarystructures, as exemplified by a pneumatic motor. This invention providesthe rotary apparatus with novel features for controlling a gap like thegap discussed above.

The static structure includes an end plate having a race cavity. Therotary structure includes a main rotor having a stub shaft extendingfrom one end of the main rotor. The bearing includes an outer race andan inner race. The outer race is seated in the race cavity of the endplate. The inner race has a central bore. It the bearing is a rollingcontact bearing, as exemplified by a ball bearing, the bearing alsoincludes plural rolling elements interposed between the outer and innerraces. The stub shaft is sized so as to be inserted into the centralbore of the inner race, from an inner end of the inner race, with africtional fit.

This invention provides means having a threaded connection to the stubshaft for drawing the stub shaft into the central bore o' the inner racefor a sufficient distance to provide a controlled gap between the mainrotor and the end plate. This invention contemplates that, even if ahydraulic or mechanical press is employed to press the stub shaft partlyinto the central bore, means having a threaded connection to the stubshaft is to then be employed to draw the stub shaft further into thecentral bore.

In a preferred embodiment of this invention, a screw having a threadedshank and an integral head is employed as a means having a threadedconnection to the stub shift. The threaded shank is threadable into athreaded socket extending axially into the rotary structure and openingat a distal end of the stub shaft. The threaded shank is threaded intothe threaded socket so as to draw the stub shaft into the central boreof the inner race for a sufficient distance to provide the controlledgap between the main rotor and the end plate, whereupon the screw may beoptionally removed.

Preferably, in the preferred embodiment, a washer is interposed betweenthe screw head and the inner race, and the threaded shank is threadedinto the threaded socket until an outer face of the washer bears againstthe screw head and an inner face of the washer bears against the distalend of the stub shaft and against an outer end of the inner race. Thewasher is removable with the screw.

In an alternative embodiment, in which a threaded stud extends axiallyfrom the distal end of the stub shaft and defines a shoulder at thedistal end of the stub shaft, a threaded nut is employed as the meanshaving a threaded connection to the stub shaft. The threaded nut isthreaded onto the threaded stud so as to draw the stub shaft into thecentral bore for a sufficient distance to provide the controlled gapbetween the main rotor and the end plate, whereupon the threaded nut maybe optionally removed.

Preferably, in the alternative embodiment, a washer is interposedbetween the threaded nut and the inner race, and the threaded nut isthreaded onto the threaded stud until the washer bears against thethreaded nut, against the distal end of the stub shaft, and against theouter end of the inner race. The washer is removable with the threadednut.

This invention also provides a related method for assembling a rotaryapparatus of the type noted above, in a preferred mode for assemblingthe preferred embodiment discussed above, and in an alternative mode forassembling the alternative embodiment discussed above.

Although this invention has been applied initially to a pneumatic motor,it is contemplated that this invention may prove to be widely applicableto other rotary apparatus, whether pneumatic, hydraulic, mechanical, orelectrical.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features, and advantages of this invention willbe evident from the following description of two contemplatedembodiments of this invention with reference to the accompanyingdrawings in which like reference characters designate like orcorresponding parts throughout the several views, and wherein:

FIG. 1 is a perspective view of a rotary apparatus, such as a pneumaticmotor, of the type noted above.

FIG. 2, on a larger scale, is a fragmentary, partly cross-sectioned viewof such a rotary apparatus constituting a preferred embodiment of thisinvention.

FIG. 3, on a similar scale, is a fragmentary, partly cross-sectionedview of such a rotary apparatus constituting an alternative embodimentof this invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

As shown in FIG. 1, a pneumatic motor 10 exemplifies a rotary apparatusof the type noted above. Thus, the pneumatic motor 10 defines an axisand comprises a static structure, a rotary structure, and a bearinginterposed between the static and rotary structures.

In the preferred embodiment shown in FIG. 2 and in the alternativeembodiment shown in FIG. 3, the static structure includes an end plate20, which has a race cavity 22 with a chamfered edge 24 and which has aninner surface 26 normal to the axis defined by the pneumatic motor 10.The end plate 20 is suitably mounted within an outer housing 12, whichis shown in FIG. 1, with an O-ring 28 surrounding and sealing the endplate 20.

Further, the rotary structure includes a main rotor 30 and a stub shaft32, which extends axially from one end of the main rotor 30 and whichhas a distal end 34. The main rotor 30 and the stub shaft 32 areintegral, preferably being Machined from a single piece of aluminum. Atthe same end, the main rotor 30 has an outer surface 36, which is normalto the axis defined by the pneumatic motor 10. As shown in FIG. 1, themain rotor 30 has radial vanes 38, which are also shown in FIG. 2.

Moreover, a rolling contact bearing 40 is interposed between the staticand rotary structures. The rolling contact bearing 40 includes an outerrace 42, an inner race 44, and plural rolling elements 46 interposedbetween the outer race 42 and the inner race 44. Preferably, as shown,the outer race 42 is enclosed by an outer collar 48. As shown, therolling contact bearing 40 is a conventional ball bearing, in which therolling elements 46 are balls.

The outer race 42, as enclosed by the outer collar 48, is seated in therace cavity 22 of the end plate 20. A hydraulic or mechanical press (notshown) is employed to press the outer race 42, as enclosed by the outercollar 48, fully into the race cavity 22 with an interference fit. Thechamfered edge 24 facilitates initial entry of the cuter race 42, asenclosed by the outer collar 48, into the race cavity 22.

The inner race 44 has a central bore 50. The stub shaft 32 is sized soas to be inserted into the central bore 50, through an inner end 52 ofthe central bore 50, with an interference fit. The distal end 34 of thestub shaft 32 is chamfered, as shown, so as to facilitate initial entryof the stub shaft 32 into the central bore 50.

It is contemplated by this invention to employ such a press to press thestub shaft 32 partly but not fully into the central bore 50 and toemploy means having a threaded connection to the stub shaft 32 to drawthe stub shaft 32 further into the central bore 50. It is also iscontemplated by this invention to employ means having a threadedconnection to the stub shaft 32 to draw the stub shaft 32 initially andfurther into the central bore 50. In either instance, the stub shaft 32is drawn into the central bore 50 for a sufficient distance to provide acontrolled gap g within a narrow range of tolerances (such as forexample 0.05 mm to 0.10 mm) between the outer surface 36 of the mainrotor 30 and the inner surface 26 of the end plate 20.

In the preferred embodiment shown in FIG. 2, a screw 60 having athreaded shank 62 and having an integral head 64 with a driving socket66 to accommodate a driving tool (not shown) and an annular washer 70having an outer surface 72 and an inner surface 74 are employed to drawthe stub shaft 32 into the central bore 50. The threaded shank 62 isthreadable into a threaded socket 80 extending axially into the rotarystructure, opening at the distal end 34 of the stub shaft 32. As shownin FIG. 2. the threaded socket 80 extends through the stub shaft 32,into the main rotor 30.

For assembling the preferred embodiment, a driving tool coacting withthe driving socket 66 in the screw head 64 is used to drive the screw 60so that the threaded shank 62 is threaded into the threaded socket 80.The threaded shank 62 is threaded into the threaded socket 80 until theouter surface 72 of the washer bears against the screw head 64 and theinner surface 74 of the washer 70 bears against the distal end 34 of thestub shaft 32 and against an outer end S2 of the inner race 44, so as todraw the stub shaft 32 into the central bore 50 for a sufficientdistance to provide the controlled gap g between the outer surface 36 ofthe main rotor 30 and the inner surface 26 of the end plate 20,whereupon the screw 60 and the washer 70 may be optionally removed.

In the alternative embodiment shown in FIG. 3, a threaded stud 90extends axially from the distal end 34 of the stub shaft 32, so as todefine a shoulder 92 at the distal end 34 where the distal end 34 ischamfered. As shown, the threaded stud 90 is integral with the stubshaft 32 and the main rotor 30, preferably being machined from a singlepiece of aluminum. Alternatively, the threaded stud 90 is a separatepiece, a portion of which is threaded into a threaded socket (not shown)similar to the threaded socket 80 of the preferred embodiment. Thethreaded stud 90, a threaded nut 100, and a washer 110 having an outerface 112 and an inner face 114 are employed to draw the stub shaft 32into the central bore 50. The washer 110 is interposed between thethreaded nut 100 and the outer end 82 of the inner race 44.

For assembling the alternative embodiment, a wrench (not shown) is usedto thread the threaded nut 100 onto the threaded stud 90 until the outerface 112 of the washer 110 bears against the threaded nut 100 and theinner face 114 of the washer 110 bears against the shoulder 92 at thedistal end 34 of the stub shaft 32 and against the outer end 82 of theinner race 44, so as to draw the stub shaft 32 into the central bore 50until the controlled gap g is provided between the outer surface 36 ofthe main rotor 30 and the inner surface 26 of the end plate 20,whereupon the threaded nut 100 and the washer 120 say be optionallyremoved. Moreover, if the threaded stud 90 is a separate piece, thethreaded stud 90 may be optionally removed with the threaded nut 100 andthe washer 110.

Advantageously, either of the preferred and alternative embodimentsdescribed above enables the gap g to be precisely controlled withoutemploying gauges when the rotary apparatus is assembled. As an example,threads designated M6×1.0 mm provide axial movement of one millimeterper 360° of rotation.

Various modifications may be made in the preferred and alternativeembodiments described above without departing from the scope and spiritof this invention. It is therefore to be understood that within thescope of the appended claims, the present invention may be practicedotherwise than as specifically described herein.

I claim:
 1. A method for assembling a rotary apparatus, comprising thesteps of:providing a static structure comprising an end plate having arace cavity defined therein; providing a rotary structure having arotary axis and a rotor, having a stub shaft extending from one end ofsaid rotor, rotatable about said rotary axis; interposing a rollingcontact bearing, comprising an outer race and an inner race, betweensaid end plate of said static structure and said stub shaft of saidrotary structure, so as to permit said rotary structure to rotaterelative to said static structure, by seating said outer race withinsaid race cavity of said end plate; providing said inner race with acentral bore, an outer end, and an inner end; providing said stub shaftwith a distal end which is sized so as to be inserted into said centralbore of said inner race, in a direction extending from said inner end ofsaid inner race toward said outer end of said inner race, with africtional fit; providing said stub shaft with a threaded socket whichextends axially into said stub shaft from said distal end thereof; andthreading a screw, having a threaded shank, into said threaded socket ofsaid stub shaft, thereby moving said stub shaft into said central boreof said inner race until a controlled gap is provided between said rotorand said end plate.
 2. The method of claim 1 wherein the screw isremoved after the controlled gap has been provided between the rotor andthe end plate.
 3. The method of claim 1, further comprising the stepsof:providing said screw with a head integral with said threaded shank;interposing a washer between said screw head and said outer end of saidinner race; and threading said threaded shank of said screw into saidthreaded socket of said stub shaft until said washer bears against saidscrew head, against said distal end of said stub shaft, and against saidouter end of said inner race.
 4. The method of claim 3 wherein the screwand the washer are removed after the controlled gap has been providedbetween the rotor and the end plate.
 5. The method of claim 1 whereinthe bearing includes plural rolling elements interposed between theouter and inner races.
 6. The method as set forth in claim 5,wherein:said plural rolling elements comprise ball elements.
 7. Themethod as set forth in claim 1, wherein:said outer race is seated withinsaid cavity of said end plate by an interference fit.
 8. The method asset forth in claim 1, wherein:said controlled gap comprises a dimensionwithin the range of 0.05-0.10 mm.
 9. The method as set forth in claim 1,further comprising the step of:providing said stub shaft and said rotoras a single, integral component by machining said rotor and said stubshaft there-of from a single piece of metal.
 10. The method as set forthin claim 1, wherein:the rotary apparatus is formed as a pneumatic motor.11. A method for assembling a rotary apparatus, comprising the stepsof:providing a static structure comprising an end plate having a racecavity defined therein; providing a rotary structure having a rotaryaxis and a rotor, having a stub shaft extending from one of said rotor,rotatable about said rotary axis; interposing a rolling contact bearing,comprising an outer race and an inner race, between said end plate ofsaid static structure and said stub shaft of said rotary structure, soas to permit said rotary structure to rotate relative to said staticstructure, by seating said outer race within said race cavity of saidend plate; providing said inner race with a central bore, an outer end,and an inner end; providing said stub shaft with a distal end which issized so as to be inserted into said central bore of said inner race, ina direction extending from said inner end of said inner race toward saidouter end of said inner race, with a frictional fit; providing said stubshaft with a threaded stud extending axially from said distal end ofsaid stub shaft; and threading a threaded nut onto said threaded stud ofsaid stub shaft, thereby moving said stub shaft into said central boreof said inner race until a controlled gap is provided between said rotorand said end plate.
 12. The method as set forth in claim 11, furthercomprising the steps of:interposing a washer between said threaded nutand said outer end of said inner race; and threading said threaded nutonto said threaded stud of said stub shaft until said washer bearsagainst said threaded nut, against said distal end of said stub shaft,and against said outer end of said inner race.
 13. The method as setforth in claim 12, further comprising the step of;removing said threadednut and said washer from said threaded stud of said stub shaft aftersaid controlled gap has been provided between said rotor and said endplate.
 14. The method as set forth in claim 11, further comprising thestep of:removing said threaded nut from said threaded stud of said stubshaft after said controlled gap has been provided between said rotor andsaid end plate.
 15. The method as set forth in claim 11, furthercomprising the step of:providing a plurality of rolling elements in saidrolling contact bearing between said inner and outer races thereof. 16.The method as set forth in claim 15, further comprising the stepof:providing ball elements as said plurality of rolling elements withinsaid rolling contact bearing.
 17. The method as set forth in claim 11,further comprising the step of:seating said outer race within saidcavity of said end plate by an interference fit.
 18. The method as setforth in claim 11, further comprising the step of:providing saidcontrolled gap with a dimension which is within the range of 0.05-0.10mm.
 19. The method as set forth in claim 11, further comprising the stepof:providing said stub shaft, said threaded stud, and said rotor as asingle, integral component by machining said rotor, said stub shaft, andsaid threaded stud from a single piece of metal.
 20. The method as setforth in claims 11, wherein:said rotary apparatus is formed as apneumatic motor.
 21. A method of assembling a rotary apparatus,comprising the steps of:providing a static structure comprising an endplate having a race cavity defined therein; providing a rotary structurehaving a rotary axis and a rotor, having a stub shaft extending from oneend of said rotor, rotatable about said rotary axis; interposing arolling contact bearing, comprising an outer race and an inner race,between said end plate of said static structure and said stub shaft ofsaid rotary structure, so as to permit said rotary structure to rotaterelative to said static structure, by seating said outer race withinsaid race cavity of said end plate; providing said inner race with acentral bore, an outer end, and an inner end; providing said stub shaftwith a distal end which is sized so as to be inserted into said centralbore of said inner race, in a direction extending from said inner end ofsaid inner race toward said outer end of said inner race, with africtional fit; providing said stub shaft with a first threadedcomponent and providing a second threaded component for threadedengagement with said first threaded component of said stub shaft,thereby moving said stub shaft into said central bore of said inner raceuntil a controlled gap is provided between said rotor and said endplate.
 22. The method as set forth in claim 21, wherein:said firstthreaded component of said stub shaft comprises a threaded socket; andsaid second threaded component comprises a threaded screw having athreaded shank for threaded engaging said threaded socket of said stubshaft.
 23. The method as set forth in claim 21, wherein:said firstthreaded component of said stub shaft comprises a threaded stud; andsaid second threaded component comprises a threaded nut for threadedlyengaging said threaded stud of said stub shaft.